Steel is the pre-eminent metal for designing and manufacturing cars. It is used to manufacture the body panels. The main reasons that steel is used as oppose to other materials is that it is cheap to produce, widely available, ductile and malleable, strong, has a high young modulus and has high impact absorbing qualities.               

The table below shows the main properties that a material needs in order for it to be suitable for car body panels.

The specification for car body panels are that they need to be strong, hard and tough enough to protect the passengers. However, they also have to be ductile, light and cheap enough to be practical. So the material needs to have a high young modulus, toughness, strength, hardness and ductility whilst being light and low in price.

The five materials in the table all have certain properties that fit the specification and other properties that don't. The material used in car body panels, mild steel, is the one with the most suitable overall properties that fit the specification. It has a high young modulus, it is tough, ductile, strong, cheap and reasonably light.

Another reason why steel is used is that It has an inherent capacity to absorb impact and thus diffuse crash energy. Steel, for example, becomes harder when it is crushed, which means it becomes stronger, increasing the amount of energy it can absorb. This means that in and accident steel will protect the occupants of the vehicle and help to prevent
injury.